What isn't too confusing then? Markdown and HTML are just riffs, it's all based around the idea of opening/closing tokens and special tag names that do different things. I think if there is in fact a technical barrier, then it's the underlying fact that your representation of a document has a separation of content and design/layout. If people can't deal with that, then they can only use WYSIWYG (and not the hacks of rendering to the side while you still type in TeX), and there's no point in trying to update LaTeX's notation to fit people who never will get that underlying separation.
Markdown has its own magic incantations that can infuriate if you don't get them just right. GP is right: most people can't handle markup languages, period. Or, they can, but vastly prefer WYSIWYG text formatting.
For me, if I'm writing something for a web page, I use HTML in a decent editor (emacs). Markdown, reST, or anything else is not easier, just different.
If I need a really nice-looking document, I'll probably use LaTeX. But for a simple document or one that I'll work on with other people, I'll normally just use google docs.